分布式双向中继系统的安全总速率优化
Secrecy Sum Rate Optimization of Distributed Two-Way Relay Systems

研究了分布式双向中继系统中的安全传输问题。为了优化系统总功率约束下的安全总速率，提出了基于人工噪声辅助的波束形成(Artificial-noise-aided beamforming,ANBF)发射方案。在ANBF方案中，待解决的问题是一个非凸的优化问题。为了求解该问题，分别采用连续参数凸近似算法(Sequential parametric convex approximation,SPCA)和牛顿迭代法，对波束形成向量，人工噪声的协方差矩阵和源节点发射功率进行交替优化迭代求解，最终得到局部最优解。可以证明，已有的未加人工噪声的常规波束形成(Beamforming,BF)方案和零空间波束形成(Null-space BF,NSBF)方案是ANBF方案的特例，后者使系统设计更具一般性。在仿真实验中，对比了ANBF方案与常规BF方案以及NSBF方案的安全性能，实验结果和性能分析验证了本文所提ANBF方案的有效性，并表明它具有最优的安全性能。
The secure transmission of distributed two-way relay systems is studied. To maximize the secrecy sum rate subject to the aggregate power constraint, an artificial-noise-aided beamforming (ANBF) scheme is proposed. The major difficulty in the ANBF scheme is a non-convex optimization problem. Therefore, a sequential parametric convex approximation (SPCA) algorithm is proposed, together with a New ton iteration method, to optimize the beamforming vector, artificial noise covariance matrix as well as the transmission power in an alternating iterative way. The ANBF scheme is proved to be a generalization of the existing beamforming (BF) scheme without AN and the null space beamforming (NSBF) scheme, and the system design is more universal. Simulation results and performance analysis verify t he efficiency of the proposed ANBF scheme, and reveal that it achieves the highest secrecy sum rate.